R. Yoshida

Description and performance of the Fermilab E687 spectrometer

Abstract The magnetic spectrometer and charged particle tracking system used in Fermilab experiment 687 to study the photoproduction and decay of charm particles are described in detail. The photons are produced by a wideband electron beam which can operate at energies up to 600 GeV/ c . The spectrometer consists of a high resolution silicon microstrip detector, a large aperture dipole magnet, proportional chambers, a second large aperture dipole, and more proportional chambers. Three multi-cell threshold Cherenkov counters provide charged particle identification. The tracking system is capable of resolving the secondary decay vertices of charm and beauty mesons and baryons from the primary interaction vertex. It also determines the invariant mass of the multibody final states of particles containing heavy quarks with excellent resolution. The particle identification system allows one to identify kaons and protons present in these final states clearly. This collection of detectors produces very clean signals for charm particles and permits one to make many cross checks of the apparatus. The performance is illustrated for a variety of charm signals. Of particular interest is a description of the tracking through the silicon microstrip detector and its use in isolating downstream decay vertices. Two complementary approaches to the reconstruction of secondary decay vertices are presented and insight is gained by comparing their strengths and weaknesses.

Analysis of the decay mode D+ → K∗0μ+ν

Abstract Fermilab high-energy photoproduction experiment E687 provides a high statistics sample of the decay mode D + → K ∗0 μ + ν (charge conjugates are implied). Our analysis yields a branching ratio of Γ (D + → K ∗0 μ + ν) Γ (D + → K − π + π + ) = 0.56±0.04±0.06 . The ratios of the form factors governing the decay are measured to be R ν = 1.74 ±0.27±0.28 and R 2 = 0.78±0.18±0.10, implying a polarization of Γ l Γ t = 1.20±0.13 ±0.13 for the electron decay. Finally, we report new limits on the decay modes D + → K − π + μ + ν (nonresonent) and D + → K ∗0 π 0 μ + ν .

Analysis of the decay mode D+ ---> anti-K*0 mu+ neutrino

Abstract Fermilab high-energy photoproduction experiment E687 provides a high statistics sample of the decay mode D + → K ∗0 μ + ν (charge conjugates are implied). Our analysis yields a branching ratio of Γ (D + → K ∗0 μ + ν) Γ (D + → K − π + π + ) = 0.56±0.04±0.06 . The ratios of the form factors governing the decay are measured to be R ν = 1.74 ±0.27±0.28 and R 2 = 0.78±0.18±0.10, implying a polarization of Γ l Γ t = 1.20±0.13 ±0.13 for the electron decay. Finally, we report new limits on the decay modes D + → K − π + μ + ν (nonresonent) and D + → K ∗0 π 0 μ + ν .

A measurement of elastic J/ψ photoproduction cross section at Fermilab E687☆

Abstract Measurements of elastic photoproduction cross sections for the J / ψ meson from 100 GeV to 375 GeV are presented. The results indicate that the cross section increases slowly in this range. The shape of the energy dependence agrees well with the photon-gluon fusion model prediction.

Studies of DD correlations in high energy photoproduction

Abstract Analysis of data from the Fermilab high energy photoproduction experiment E687 for events containing fully and partially reconstructed pairs of charmed mesons is presented. Correlations from D D pairs are used to study production dynamics.

Measurement of Λ+c and D+s lifetimes☆

Abstract Measurements of the lifetimes of the Λ+c decaying into pK−π+ and of the D+s decaying into φπ+ are presented. The data were accumulated in the Fermilab Wide-Band photoproduction experiment E687. The lifetimes of the Λ+c and the D+s are measured to be (0.20±0.03±3)× 10−12s and (0.50±0.06±0.03) × 10−12s respectively.

Study of D0 → K−μ+ν in high energy photoproduction

Abstract We report a measurement of the semimuonic decay D0→K−μ+ν from data taken during the 1987–1988 fixed target run at Fermilab by the E687 Collaboration. We obtain Γ(D0→K−μ+ν)/Γ(D0→K−π+)=0.82±0.13±0.13 and use this result to calculate Γ(D 0 →K ∗− μ + ν)/Γ(D 0 →K − μ + ν)=0.59±0.10±0.13 .

Measurement of the decays D0 → π+π+π−π−, D0 → K−K+ and D+s → фπ+π+π−

Abstract We present measurements of the branching ratios for two Cabibbo suppressed decays of the D 0 meson, D 0 → π + π + π − π − and D 0 → K − K + , and for the decay D + s → фπ + π + π − . The physics signals were extracted from a data sample consisting of 60 million triggers, collected by Fermilab Photoproduction Experiment E687 from December 1987 to February 1988. The relative branching ratios are measured to be: Γ (D 0 → 4 π )/ Γ (D 0 → K3 π ) = 0.108±0.024±0.008, Γ (D 0 → KK)/ Γ (D 0 → K π ) = 0.138±0.027 ±0.010 and Γ( D s → ф3π)/Γ( D s → фπ) = 0.58±0.20±0.10 .

Performance of the hadron calorimeter for fnal experiment E687

Abstract A sampling gas hadron calorimeter with tower readout geometry has been constructed for a photoproduction experiment, E687, at Fermilab. This experiment has run in the Wide Band photon beam with photons of maximum energy of 450 GeV. The calorimeter consists of 28 120×82×1.75 in. Fe plates interspersed with planes of extruded aluminum proportional tubes. Capacitively induced signals on electrode pads with a cylindrical geometry are read out. The preamplifier and shaping electronics, constructed from surface mount devices, are mounted on the detector. The system has a dynamic range that spans the region from minimum ionizing particles (mip) to a few hundred mips. Calibrating the system response was done using muons, electronic test signals, and by recording the pulse height of an 55 Fe source with a proportional counter. Results on the details of the performance of the calorimeter and its use as an online trigger are described.

A Monte Carlo procedure for Bethe-Heitler production of dileptons with high invariant mass

Abstract A Monte Carlo procedure for the Bethe-Heitler production process, when the invariant mass of the produced leptons are high ( > 1 GeV), has been developed. The procedure can be tuned to simulate events above a chosen invariant mass and have been used both for acceptance study and calculation of the cross section in J/ψ photoproduction where Bethe-Heitler dimuon production is the dominant background.